Mr Eavis said: "It was obvious from our telephone conversation that U2 are hugely disappointed. Clearly they were looking forward to playing the Pyramid Stage as much as we were looking forward to watching them."

'Best wishes'

He declined to comment on a possible replacement. "Instead, we would simply like to send Bono our very best wishes for a full and speedy recovery," Mr Eavis added.

Dizzee Rascal, who is below U2 on the Pyramid Stage bill on Friday 25 June, could now take the headline slot. Festival favourites Coldplay have also been mentioned as possible replacements.

The festival has had to cope with headliners pulling out in the past.

In 1995, The Stone Roses cancelled when guitarist John Squire broke his collarbone in a cycling accident. Pulp were brought in as last-minute replacements.

In 2005, Kylie Minogue withdrew following her diagnosis with breast cancer. Basement Jaxx were promoted to fill in.

U2's North American dates will be rescheduled.

Their 360 Degree tour earned the band about $109m (£75.3m) in 2009, making it the most profitable tour of the year, according to Billboard magazine.